Portable electronics, electric vehicles, and stationary electricity storage drive demand for rechargeable batteries with high energy densities. Batteries that use Li as a mobile ion have dominated these markets. Lithium ion batteries deliver a combination of energy, power, lifespan, safety, and affordability. Therefore, the growth of rechargeable batteries with high energy densities is linked to the availability of Li.
Most global Li resources are found in brines. The conventional method for extracting Li from a brine comprises a sequence of steps to remove various elements from the brine prior to precipitation of Li2CO3. (e.g., P. Meshram, B. D. Pandey and T. R. Mankhand, Hydrometallurgy, 2014, 150, 192-208.) First, the brine is concentrated through solar evaporation to precipitate NaCl and KCl. Next, Mg, Ca, and other impurities are removed from the brine through a variety of separation processes. (e.g., J. W. An, D. J. Kang, K. T. Tran, M. J. Kim, T. Lim and T. Tran, Hydrometallurgy, 2012, 117-118, 64-70.) Finally, Li is precipitated as Li2CO3 by addition of soda (Na2CO3).
Li ion exchange is an alternative process for extracting Li from brines. In this approach, Li is selectively removed from a brine in the presence of other elements; therefore, various steps to remove other elements from the brine are avoided. The Li ion exchange process is based on materials that can absorb and release Li according to changes in pH. When pH is low, these materials absorb H and release Li. When pH is high, the materials absorb Li and release H.
A limited variety of compounds for Li ion exchange have been demonstrated. Li extraction from brines has been demonstrated using LiMn2O4, Li4/3Mn5/3O4, Li1.6Mn1.6O4, and Li2TiO3. (See, K. Ooi, Y. Miyai and J. Sakakihara, Langmuir, 1991, 7, 1167-1171; A. Umeno, Y. Miyai, N. Takagi, R. Chitrakar, K. Sakane and K. Ooi, Ind. Eng. Chem. Res., 2002, 41, 4281-4287; R. Chitrakar, H. Kanoh, Y. Miyai and K. Ooi, Chem. Mater., 2000, 12, 3151-3157; and R. Chitrakar, Y. Makita, K. Ooi and A. Sonoda, Dalton Trans., 2014, 43, 8933.)